This invention relates generally to shim material and more particularly to a plastic shim adapted for application between two spaced surfaces.
Shims have been used for many years to provide proper spacing between two surfaces, provide a seal between two mating surfaces, or to adjust the height or position of a particular object spaced from another object. Shims are used in a variety of manufacturing operations to fill unwanted gaps or spaces in assembled articles caused by imperfectly fitting components. For example, in the automotive industry, steel shims are commonly used to fill gaps during the assembly of various components where subassemblies are bolted together. In other industries shims are used to compensate for alignment irregularities between mating surfaces and to adjust the orientation of a structure.
In large machinery mounting applications, a bed plate is typically formed and the machine is mounted on the bed plate via studs or bolts. The machine is leveled by placing shims of appropriate thicknesses between the machine base and the bed plate. A worker mounting a large piece of machinery such as a generator or an air conditioning unit, must place various sizes of shims between the unit base and the foundation. In situations where the foundation does not have upwardly projecting studs, positioning a shim between the mating surfaces may be difficult and possibly dangerous to the worker. If the piece of machinery is particularly heavy, positioning a loose shim correctly on the foundation is difficult. Often the shim moves from the desired position as the components are mated together requiring several attempts at proper placement of the shims. These conventional shims are usually metal and are relatively heavy, expensive and often prone to corrode.
In manufacturing situations where shims are required, it is desirable to be able to place a shim against one surface such that the shim remains against the surface until the other mating surface is joined. However, when using conventional shims the first surface must generally be upwardly facing with projecting pins or studs projecting upward so that when the shim is placed over the studs and onto the surface gravity retains the shims in position. Otherwise, if this first surface is slanted or downwardly facing, a conventional shim placed thereon will simply fall off.
Accordingly, it is a principal object of this invention to provide a plastic shim to overcome this disadvantage and to provide shims that are lightweight, rust free, simple to install, and will retain their position against a surface having a projection outward therefrom in any orientation until the two mating surfaces are joined.
A self retaining plastic shim according to the present invention has a generally flat plate shape with an aperture therethrough. The shim has integral opposing tabs projecting inward from the wall of the aperture. These tabs are preferably of decreasing thickness as the tab extends inward of the aperture. The tabs elastically deflect when a shim having these tabs is placed onto a surface having a projection such as a stud pushed through the aperture in the shim. The deflection of the tabs against the stud holds the shim in place against the surface of the first body until the first body with the shim attached is placed against a second body having a corresponding aperture to receive the bolt or stud.
Thus when the shim is simply applied to one surface having projecting studs, bolts or pins, it is unnecessary to manually hold the shim in place while the two surfaces are joined.
Further objects, features and advantages of the invention will become evident from a consideration of the following detailed description when taken in conjunction with the accompanying drawing and the appended claims .